Picture frames made from cardboard blanks have been described, for example, in U.S. Pat. No. 2,814,896 (Fujikawa) 3 Dec. 1957. Existing designs suffer from various problems. The frame is typically of a fixed size and aspect ratio, whereas frames of various dimensions may be required. Folded card frames also lack structural rigidity. Such a frame is too large to be posted even in flat form. This type of frame is also expensive to produce due to the size of the blank and complexity of the cutting tool required.
A box frame is a deep frame into which, for example, a stretched canvas on a wooden frame can be inserted. A few mm clearance between the outer mouldings of the frame and the canvas is required so that the art can be inserted and removed and repositioned.
U.S. Pat. No. 796,310 (Fisher) 1 Aug. 1905 describes in one embodiment a frame assembled from a base card and four blanks which define triangular or rectangular mouldings. The blanks are of different designs for the short and long sides and the size of the frame is constrained by the base plate. Assembly also requires complex manipulation of slits and tabs to interconnect the base and moulding blanks.